But their road trip was cut short just miles outside Los Angeles, the police said he told them. The couple got into an argument, he said, and he let Ms. Shabani out of the car in Santa Clarita, a city about 25 miles from her apartment. However, detectives found no signs of Ms. Shabani in Santa Clarita or in Yuba County, where his father lives, Captain Hayes said on Tuesday.

By early March, friends still had not heard from Ms. Shabani, who was born in Macedonia and went to high school there. She attended college at the American University of Paris, according to her Facebook profile, and then moved to Hollywood to pursue a career in acting and modeling. She played a small role in an independent movie released last year.

Around that same time in March, Mr. Spotz left California with his fiancée for Fort Morgan, Colo. The Los Angeles Police Department alerted other police agencies that they were searching for Mr. Spotz and his Toyota Tacoma pickup truck.

Last Thursday, San Bernardino sheriff’s deputies spotted his pickup truck near Interstate 10 east of Los Angeles. They tried to stop him, but Mr. Spotz took off, leading them on a roughly 60-mile chase that ended when he fatally shot himself inside the truck, the police said.

Captain Hayes said that despite the department’s frantic search for Ms. Shabani in late February, she was most likely dead the same day she left her apartment or the next morning. “Something happened, and I believe it to be somewhat untoward — that there was foul play involved,” he said at the news conference.

Captain Hayes did not say how she died, though he noted that detectives believe Mr. Spotz played some role in her death, which was being investigated as a homicide. “I do believe he was involved in it,” he said.

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